Bioremediation

Event Date: 
Wednesday, June 26, 2013 - 18:00 - 18:15
Institution: 
UNSW
Title: 

Towards a hexachlorobenzene bioreactor

Abstract: 

Hexachlorobenzene (HCB) is highly persistent environmental pollutant due to its chemical stability. It has been used in the production of rubber, as wood preserving agent and as pesticide and it is considered a possible human carcinogen.  HCB is particularly relevant in Australia, since it holds the largest HCB stockpile in the world (Botany Bay Industrial Park, NSW). So far only physic-chemical technologies have been applied for the destruction of HCB; however, these methods do not ensure full destruction and may lead to the generation of more harmful compounds, such as dioxins.  On the other hand, it is well known that obligate anaerobic bacteria are able to reductively dechlorinate HCB to less chlorinated congeners.  Therefore, a biological approach seems to be a more suitable and environmental friendly solution.

In this study we present a microbial community, taken from a site contaminated with chlorinated solvents, capable of reductively dechlorinating HCB and 1,2,4,5- Tetrachlorobenzene (TeCB). Cultures were established using acetate and H2 or lactate as carbon source and electron donor, respectively. 1,3- and 1,4- dichlorobenzenes were the main breakdown products in the cultures supplied  with 1, 2, 4, 5- TeCB, monochlorobenzene was also observed in a lower extent. Cultures with HCB only showed  1, 3, 5-Trichlorobenzene as breakdown product. Quantitative PCR, targeting Dehalococcoides´ 16S (a well-known dechlorinating bacterium) showed high abundance of this species in the cultures. 

JAMS REPORT
Ani Penesyan
 
On the last Wednesday of spring we were spoiled with the room on the top floor of the Australian Museum and magnificent views of Sydney, yes, once again! Joining us were not only our regular JAMS crowd, but also visitors from Europe (yes, that is really cold in Europe during this time of the year!)
 

Event Date: 
Wednesday, November 28, 2012 - 07:00 - 08:00
Institution: 
University of Sydney
Title: 

Biodegradation of dichloroethane by aerobic bacteria at the Botany Industrial Park

Abstract: 

The chlorinated hydrocarbon 1,2-dichloroethane (DCA) is a common pollutant of groundwater, and poses both human and environmental health risks. The Botany Industrial Park in south Sydney is heavily contaminated with DCA and other organochlorines. The main user of the site (Orica Ltd) operates a large groundwater treatment plant (GTP) on site to contain and remediate the DCA-contaminated groundwater. At present, remediation is done by air-stripping and thermal oxidation, but this is very costly and energy-intensive. Orica is interested in alternative technologies for treating the groundwater, including bioremediation. In 2010, a pilot scale membrane bioreactor (MBR) was set up to treat a fraction of the groundwater. The aims of our study were to identify DCA-degrading bacteria and genes in the GTP and on the site at large, define the community structure and ecological successions occurring in the MBR, develop a qPCR for catabolic genes in the DCA biodegradation pathway, and field-test this qPCR assay in the MBR and in a survey of groundwater in monitoring wells on the site. We discovered that DCA-degrading bacteria using a hydrolytic pathway (dhlA/dhlB genes) were widespread and diverse at this site, and that the dhlA gene was carried on a catabolic plasmid. The community in the MBR was dominated by alpha- and beta-proteobacteria, and was highly dynamic, changing dramatically in composition as the percentage of raw groundwater in the feed was increased. By combining dhlA qPCR and 16S pyrosequencing data, we found evidence that thus-far-uncultured species of Azoarcus may play a major role in DCA bioremediation in situ in the MBR.

Event Date: 
Wednesday, October 31, 2012 - 07:00 - 08:00
Institution: 
CSIRO
Title: 

Microbial responses to phenanthrene contamination in soil

Abstract: 

 
The effect of phenanthrene on soil microbial community structure and gene expression was evaluated by 16S rRNA gene microbiome analysis and next generation sequencing of community mRNA. Widespread changes in microbial diversity and functional gene content were revealed. Actinobacteria abundances increased markedly with the addition of phenanthrene, in particular that of Arthrobacter and Mycobacterium, and evidence was also obtained for an increase in the abundance of protozoans. The abundance of transcripts annotated as dioxygenases, heavy metal P-type ATPases, thioredoxins and heat shock proteins increased 1.8-7 fold upon phenanthrene amendment, whereas those of general metabolism were little affected. Custom databases constructed with bacterial or fungal PAH metabolism genes were used to further annotate transcripts, and revealed that increases in PAH-degradatory gene expression occurred for all gene groups investigated. Taxonomic determination of mRNA transcripts showed that the actinobacteria were responsible for most of the de novo expression of transcripts associated with dioxygenases, stress response and detoxification genes. This study is the first combining microbiome and metatranscriptomic approaches to describe microbial community responses to a pollutant in soil, offering information on novel in-situ effects which opens up new directions for research in PAH degradation and bioremediation. 

 
Prepared by Valentina Wong (UNSW PhD student)
On a cold Tuesday night, Adrian Low from University of New South Wales warmed the JAMS audience with his passion on bioremediation of organochlorine contaminated groundwater. Adrian described the discovery of Australia’s first 1,2-dichloroethane (DCA) degrading consortium, AusDCA. His work in the field demonstrated the efficacy and sustainability of using organochlorine respiring bacteria to remediate organochlorine contaminants in situ. He plans to isolate the bacterial species responsible for performing this unique task.

Event Date: 
Tuesday, July 24, 2012 - 18:15 - 18:30
Institution: 
University of NSW
Title: 

Development of an Australian 1,2-Dichloroethane degrading culture

Abstract: 

 
1,2-Dichloroethane (DCA) is one of the most common organochlorine groundwater contaminants worldwide. The successes of bioremediation field studies with organochlorine respiring bacteria have proved the efficacy of the method to degrade such contaminants in situ. The objective of this study was to demonstrate that a DCA degrading consortium, named AusDCA could be used to bioaugment a DCA contaminated acidic aquifer in situ. Functional characterisation experiments of AusDCA in batch cultures showed that the culture could dechlorinate high concentrations of DCA (6.3 mM) to ethene anaerobically at pH 5.5 and pH 6.5 and was not inhibited by approximately 15 µM of chloroform (CF). 

Event Date: 
Tuesday, July 24, 2012 - 18:00 - 18:15
Institution: 
University of NSW
Title: 

Bioremediation of Mixed Chlorinated Solvents by Combining Two Biogeochemical Processes

Abstract: 

Chloroethenes are a class of chlorinated solvents which cause extensive soil and groundwater contamination worldwide. They can be detoxified by anaerobic dehalogenating bacteria, in the process of reductive dechlorination.  However, chloroethenes are often found mixed with chloromethanes, a class of solvents which inhibit the enzymatic detoxification of chloroethenes by dehalogenating strains.  Iron sulfides are powerful chemical reductants for the dechlorination of chloromethanes, and can be generated through the metabolism of iron- and sulfate-reducing bacteria. In this study, a sulfate reducing bacterium was used to produce iron sulfide in the presence of moderate levels of tetrachloroethene and carbon tetrachloride to examine the ability of a sulfate reducing organism to drive reduction of a chloromethane in the presence of chloroethene.

 

Cultures of the sulfate-reducer Desulfovibrio vulgaris were established in the presence of 100 µM each of tetrachloroethene and carbon tetrachloride. Growth, sulfide formation and chlorinated solvents and their dechlorinated products were monitored. The effects of amorphous iron oxide and cyanocobalamin on the fate of chlorinated solvents compared with unamended control cultures were investigated. 

Following growth and sulfide formation, carbon tetrachloride was dechlorinated mostly to carbon disulfide while tetrachloroethene was dechlorinated to trichloroethene and acetylene.  Dechlorination rates were enhanced both by the presence of iron and cyanocobalamin separately, and significantly increased when both were present.

This study illustrates the potential to use sulfate reducing bacteria in zones of mixed chlorinated solvent groundwater pollution in order to produce iron sulfide minerals. Their cyanocobalamin-catalyzed action on chloromethanes, coupled with that of dehalogenating strains on chloroethenes is a promising strategy for the bioremediation of such contaminated areas."

Report by Jeff Powell

On 12 April, the 'cowboys' at the Hawkesbury Institute for the Environment played host to the 'aliens' from the Sydney region for JAMS Goes West. The mood was both enthusiastic and informative and approximately 30 people participated. The morning consisted of five short talks by representatives of five Sydney-based institutions.

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